Liquid level detecting apparatus

ABSTRACT

A liquid level detecting apparatus detects a level of the surface of the supplied liquid by use of a liquid level sensing and detecting means. The apparatus comprises a fluidic device which has its input controlled in response to the liquid surface level sensed by the liquid level sensing means and thereby changes its output. Issuance of alarm, stopping of liquid supply and the like operations are performed by changing over the output of the fluidic device.

United States Patent Hisada et al. [451 Aug. 1, 1972 [54] LIQUID LEVELDETECTING [56] References Cited PARA AP TUS UNITED STATES PATENTS [72]Inventors: Takeo Hisada, Tokyo; Fumio mi Yokohama; Takes 3,277,91410/1966 Mamon ..l37/8l.5 Nislfl Tokyo; Kum Fu- BIOSSCI' et a1 jisawa,all of Japan 3,331,380 7/1967 Schonfeld ..l37/8l.5

[ Assignee: L Ke y ak t h Pn'mary Examiner-Louis R. Prince Kanagawa'kenJapan Assistant Examiner-Denis E. Corr [22] Filed: Oct. 19, 1970Attorney-Waters, Roditi, Schwartz & Nissen [21] Appl. No.: 81,922 [57]ABSTRACT A liquid level detecting apparatus detects a level of [30]Foreign Appucafion my Data the surface of the supplied liquid by use ofa liquid Oct. 29, 1969 Japan ..44/862l8 level sensing and detectingmeans, The apparatus 06L 1969 Japan comprises a fluidic device which hasits input con- L 1969 Japan "44/86220 trolled in response to the liquidsurface level sensed by Oct. 29, Japan the level Sensing means andthereby changes its output. Issuance of alarm, stopping of liquid supply[52] U.S.Cl. ..l37/81.5,73/302,116/109 and the like operations areperformed by changing [51] Int. Cl. ..G0lf 23/16 over the output of thefluidic device [58] Field of Search ..1 16/109; 73/302; 137/815 6Claims, 18 Drawing Figures PATENTEMH m2 3.680.579

SHEET 8 OF 6 FIG. I4

LIQUID LEVEL DETECTING APPARATUS This invention relates to a liquidsurface level detecting apparatus, and more particularly to an apparatusfor detecting a liquid surface level reaching a predetermined value byuse of a liquid level sensing and detecting means having a fluidicdevice or devices. The issuance of alarm, indication, or stopping ofliquid supply are performed by the output of the liquid level sensingmeans when the liquid reaches the predetermined value. 1

In general, it is necessary to detect the surface level of the suppliedliquid in order to supply a definite quantity of liquid into such acontainer as a tank or to avoid the overflow of the liquid from thecontainer. Many apparatuses have heretofore been proposed for detectingthe liquid level. An alarm or indication informing that the liquid levelhas reached at the predetermined level is provided by the leveldetecting signal. Further, the detecting signal may operate the liquidsupplying apparatus for stopping the liquid supply.

In the conventional liquid level detecting apparatus, such operations asthe liquid level detection, issuance of alarm, indication, stopping ofliquid supply and the like have been usually effective by means ofelectrical signals. However, when the liquid having its level detectedis an explosive or inflammable liquid as gasoline, the apparatus usedfor detecting the liquid level must have an explosive-proofconstruction. This sort of construction of the apparatus, however,requires a great deal of complexity and high cost.

To possibly lessen these disadvantages, there have been proposed liquidlevel detecting devices which can detect the liquid level and issueoutput signals which are converted into compressed air signals. Theoutput of this liquid level detecting signal can be varied analogously.However, in the liquid level detecting of the back pressure type inwhich the back pressure of the liquid rises in proportion to rising ofthe liquid level, the treatment of the signal is very difficult. It isrequired therefore to provide a fixed air pressure apparatus such as acomplicated pressure reducing valve for elevating the detectingaccuracy. These are disadvantages of the known liquid level detectingapparatuses.

The general object of the present invention is therefore in providing anovel and useful liquid level detectin g apparatus which eliminates thedisadvantages of the known apparatuses as hereinabove described.

Another object of the invention is to provide a liquid level detectingapparatus which can obtain an output of the liquid level detection witha digital variation to attain the liquid level detecting at a highdegree of accuracy.

A further object of the invention is to provide a liquid level detectingapparatus which can effect operations of liquid level detection,issuance of alarm, indication and stopping of liquid supply by fluidicsignals such as of air. Thereby, the detecting of the liquid can besafely performed even though it is an explosive and inflammable liquid.

A still further object of the invention is to provide a liquid leveldetecting apparatus which is simply constructed at low cost by use of adetecting means employing fluidic devices.

These and other objects and features of the invention will becomeapparent from the description with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic diagram of an embodiment of this invention;

FIG. 2 is a diagram of a fluidic circuit system in an embodiment of aliquid level detecting part of the apparatus shown in FIG. 1;

FIGS. 3A to 3C show pressure characteristics at the liquid leveldetecting part shown in FIG. 2.

FIG. 4 is a diagram of a fluidic circuit system of another embodiment ofthe liquid level detecting part in the apparatus shown in FIG. 1;

FIGS. 5A and 58 respectively show pressure characteristics at the liquidlevel detecting part shown in FIG.

FIG. 6 is a diagram of a fluidic circuit system of still anotherembodiment of the liquid level detecting part in the apparatus shown inFIG. 1;

FIG. 7 is a perspective view of a part of a shield plate used in thedetecting part of FIG. 6;

FIGS. 8A and 8B respectively show pressure characteristics at the liquidlevel detecting part of FIG. 6;

FIG. 9 is a schematic diagram of a second embodiment of the apparatus ofthe invention;

FIG. 10 is a diagram of a fluidic circuit system of an embodiment of theliquid level detecting part in the apparatus of FIG. 9;

FIG. 1 1 shows a pressure characteristic of the detecting signal of thefluidic circuit system of FIG. 10;

FIG. 12 is a schematic diagram of a third embodiment of the apparatus ofthe invention;

FIG. 13 is a side view showing two actual embodiments of the apparatusof the invention at the same time when applied in a fuel supplyingequipment for a tank lorry; and

FIG. 14 is a vertically sectioned side view showing an actual embodimentof the apparatus of the invention which is applied in a gasoline servicestation. I

FIG. 1 is a diagrammatic view schematically showing a system of a firstembodiment of the apparatus according to the present invention.Compressed air from a compressed air source 10 is supplied through anair supply pipe 11 to an air pilot spring-return type twoposition andthree-connection changeover valve 13 and through an-air supply pipe 12extending from the pipe 11 to a liquid level detecting part 14. Theliquid level detecting part 14 comprises a signal amplifier changeoverpart 15, one or more air pipes 16 and a liquid level sensing part 17.The liquid level sensing part 17 is inserted into a tank 19 of a tanklorry 18.

A detecting signal issued from the liquid level detect ing part 14 issupplied through an air pipe 20 to a pilot part 21 of the changeovervalve 13. An air-type alarm 22 is connected through an air pipe 23 tothe changeover valve 13. The aforementioned changeover valve 13, signalamplifier changeover part 15 and alarm 22 are contained in a control box24.

An embodiment of the liquid level detecting part 14 is shown in FIG. 2.The air supply pipe 12 has a fixed throttle part 30 midway thereof andis connected to a supply port 32 of a pure fluidic digit amplifierdevice 31 in the signal amplifier changeover part 41 (designated at 15in FIG. 1). An air pipe 36 extending from the output side of thethrottle part 30 of the pipe 12 has midway thereof a fixed throttle part37. The air from the pipe 36 on one hand is supplied through a pipe 38to the input (control) port 33 of the device 31. Theair from the pipe 36on the other hand is supplied, through a pipe 39 corresponding to thepipe 16 in FIG. 1; to a level sensor 40 of the bubbler tube typecorresponding to the liquid level sensing part 17 in FIG. 1.

Operations of the apparatus of the above described construction are nowdescribed. As the tank 19 is supplied with a liquid 25, the liquidsurface level rises correspondingly. Before the level of the liquid 25reaches a predetermined value, the changeover valve 13 is not yetcommunicated as shown in the figure. The compressed air from the airsource in the pipe 11 is intercepted by the changeover valve 13. Thealarm 22 is opened to the air and is not operated. The compressed airsupplied through the pipes ll, 12, 36 and 39 is discharged from anexhaust port provided at the end of the tube of the level sensor 40.

While the liquid level is low and the level sensor 40 is not yet dippedinto the liquid 25, an air pressure Pc of g the input port 33 of thedevice 31 is at a pressure Pco as shown in FIG. 38. Accordingly, the airsupplied to the supply port 32 is discharged into atmosphere from anoutput port 35. Thus, an output pressure P0 of an output port 34 ismaintained at zero as shown in FIG. 3C. The throttle part 30 is providedto set up a supply port pressure Ps so that the device 31 may comewithin an adequate range of operation. As shown in FIG. 3A, the supplyport pressure Ps is set up so as to come within an adequate operationalrange between an upper limit PS and a lower limit Ps A critical valuePcc of the input port pressure Pc must be a value such as thatcorresponding to the full line as shown in FIG. 3A according to thepressure Ps. This input port pressure Pc is set up by the throttle part37.

As the supply of liquid 25 advances and the liquid level rises so as tomake the level sensor 40 dip into the liquid 25, the air is not easilydischarged from the level sensor 40 by the head pressure of the liquidresponsive to the head height h of liquid in which the sensor is dipped.Thus, the pressure Pc of the input port 33 increases in response to thehead height h as shown in FIG. 3B. When the head height h of the liquidreaches a critical value he, the head pressure of the liquid and the airpressure in the level sensor 40 become equal and the air is notexhausted from the level sensor 40. At this instant, the input portpressure Pc reaches a critical value Pcc. As the input port pressurereaches Pcc, the output of the air supplied to the supply port 32 of thedevice 31 is instantly changed from the output port 35 to the outputport 34. The pressure P0 of the output port 34 can be digitally obtainedwith an increase of a rectangular waveform as shown in FIG. 3C.

In this embodiment, the supply port pressure Ps and the critical inputport pressure Pcc have a relationship which is expressed by the formulaPcc 1/ l0Ps.Also, the supply port pressure Ps and the output portpressure Po have a relationship of P0=3/ l OPs. Accordingly, therelationship of the pressure Po and the pressure Pcc can be shown byPo=3Pcc. Thus, in the fluidic digital amplifier device 31, the inputpressure is taken out as an output pressure amplified three times.

The air pressure signal of the pressure Po which is taken out from theoutput port 34 of the amplifier device 31, as the liquid level sensingsignal, passes through a pipe 42 (designated at in FIG. 1) and suppliedto the pilot part 21 of the changeover valve 13. This switches thechangeover valve 13 downwards against the force of a spring 26 as shownin FIG. 1. Since, in this manner, the changeover valve 13 is changedfrom a state of non-communication to a state of communication, thecompressed air from the air source 10 in the pipe 11 passes, through thechan-- geover valve 13 and pipe 23, to the alarm 22. The alarm 22thereby generates sounds, for example, of I00 phon loudness warning thatthe level of the liquid 25 has reached a height as predetermined.

The alarm 22 may not be confined to those providing alarm sounds but itmay broadly include other inform ing means such as indicators actuatedby the compressed air. According to this embodiment, the alarm 22 isdirectly operated by the air supplied from the air source 10 through thepipe, although it may indirectly operated through other means. Thecompressed air source for supplying the compressed air to the liquidlevel detecting part 14 can be separately designed from the compressedair source for supplying the compressed air to the alarm 22.

Another embodiment of the liquid level detecting part 14 is shown inFIG. 4. In FIGS. 2 and 4, identical parts being denoted by the samenumerals. An air pipe extending from the output side of the throttlepart 30 in the pipe 12 has therein a fixed throttle part 51 and extendsto a level sensor 52 (designated at 17 in FIG. 1 An air pipe 53 extendedfrom the level senser 52 is connected to the input port 33 of thefluidic digital amplifier device 31. The output port 35 of the device 31is connected through a pipe 55 (designated at 20 in FIG. 1) to the pilot21 of the changeover valve 13. The output port 34 .of the device 31 isopened to the atmosphere.

There are provided in the level senser'52 a first nozzle 56 connected tothe pipe 50 and a second nozzle 57 19 reaches a predetermined level, theshield plate 61 does not come to a position so as to shield between thenozzles 56 and 57. The air to be discharged from the nozzle 57 passesthrough the throttle part 58 and is lower in pressure than thecompressed air on the nozzle 56 side. The exhaust air port at the end ofthe nozzle 57 is affected by the pressure of jetting air injected fromthe nozzle 56. Therefore, the nozzle 57 does not exhaust the air, norcan it easily exhaust the air. Thus, the

air in the pipe 59 reduced in pressure at the throttle part 58 iscompletely or nearly completely supplied to the input port 33 of thedevice 31 through the pipe 53.

Herein, the input pressure Pc of the input port 33 is set up at thethrottle part 58 so that it can be equal to or higher than thechangeover operation critical pressure Pcc of the device 31. Then, thecompressed air supplied to the supply port 32 through the pipe 12 isdischarged from the output port 34 into the air. The output pressure P0of the output port 35 is at zero.

As the supply of the liquid 25 advances, the float 60 rises. If the headheight h of the liquid level has been raised to the fixed level he, theupper portion of the shield plate 61 provided at the float 60 shieldsbetween the nozzles 56 and 57. When the nozzles 56 and 57 are shieldedtherebetween, the nozzle 57 is opened by the jetting air injected fromthe nozzle 56 and injects the air freely. Then, the pressure of air inthe pipe 53 is lowered. The pressure Pc of the input port 33 of thedevice 31 reduces to a pressure Pco lower than the critical pressure Pccas shown in FIG. 5A. When the input port pressure Pc turns to thepressure Pco, at the instant the pressure Pc becomes lower than thepressure Pcc,the output of the device 31 is changed over instantly fromthe output port 34 to the output port 35. The output pressure P of theoutput port 35 is obtained digitally with an increase as shown in FIG.B. The output of the output port 35 is supplied to the pilot part 21 ofthe changeover valve 13 through the pipe 55, and then the changeovervalve 13 is changed in the similar way as shown in the above describedembodiment.

Still another embodiment of the liquid level detecting part 14 is shownin FIG. 6. Throughout FIGS. 2, 4 and 6,identical parts are denoted bythe same numerals. In the signal amplifier changeover part 70(designated at 15 in FIG. 1), the output port 34 of the fluidic digitalamplifier device 31 is connected with a pipe 71. The output port 35 isopened to the atmosphere.

In a level sensor 72 (designated at 17 in FIG. 1), a shield plate 73 isattached to the upper portion of the float 60. The shield plate 73 has agroove 74 at the lower part as shown in FIG. 7. Before the liquid 25reaches a predetermined level, the shield plate 73 shields between thenozzles 56 and 57 by its upper portion. The pressure Pc of the inputport 33 is lower than the critical pressure Pcc as shown in FIG. 8A. Thecompressed air supplied to the supply port 32 is discharged from theoutput port 35 to the atmosphere. The output pressure P0 of the outputport 34 is at zero.

By advance of liquid supply and with the head height h of the liquid 25reaching to a predetermined level he, the groove 74 of shield plate 73is positioned between the nozzles 56 and 57. At this instant, the nozzle57 receives the air jet injected from the nozzle 56 so that the inputport pressure Pc increases over the critical pressure Pcc as shown inFIG. 8A. Consequently, the output pressure P0 of the output port 34 issupplied through the pipe 71 to the pilot part 21 of the changeovervalve 13 with the digital rising as shown in FIG. 8B.

A second embodiment of the apparatus according to the present inventionis illustrated in FIG. 9. The compressed air from the air source issupplied through the air pipe 11 to the two-position three-connectionair changeover valve 13 of the air pilot spring return type and alsosupplied through an air pipe 80 diverged from the pipe 11 to a startingmanual operation changeover valve 81. The output side of the manualoperation changeover valve 81 is further connected through the pipe 80to an OR gate 82 including for example shuttle valve. The OR gate 82 isconnected also with an air pipe 84 diverged from an air pipe 83 on theoutput side of the changeover valve 13. The output side of the OR gate82 is connected, through an air pipe 85, to emergency stopmanually-operated changeover valve 86 and pipe 85, to the signalamplifier changeover part of the liquid level detecting part 14.

A liquid supply pipe 87 connected to a reservoir (not shown) is providedwith an air type liquid supply operating valve 88. A ball valve, poppetvalve, diaphragm valve or the like operable by a cylinder or diaphragmmay be used as the operating valve 88. The operating valve 88 is anormally closed valve which opens while its actuator is supplied withcompressed air. The air pipe 83 on the output side of the changeovervalve 13 is connected to the actuator of the operating valve 88. Anindicator 89 is connected to an air pipe 90 diverged from the pipe 83.The liquid passed through the operating valve 88 is supplied into thetank 19 by a loading arm 91. The above mentioned changeover valves 13,81 and 86, OR gate 82, signal amplifier changeover part 15 and indicator89 are contained in a control box 92.

An embodiment of the liquid level detecting part 14 used in theapparatus shown in FIG. 9 is illustrated in FIG. 10. The liquid leveldetecting part of FIG. 10 is of the similar construction as that of FIG.2. In the figure, identical parts are denoted by the same numerals, theillustration thereof being therefore omitted. The only differenceresides in that an air pipe 101 (designated at 20 in FIG. 9) isconnected to the output port 35 of the fluidic digital amplifier device31 of a signal amplifier changeover part 100(designated at 15 in FIG.19). The output port 34 is opened to the atmosphere. The fluidic device31 actuates as a NOT device in which when a predetermined input pressureis not present in the input port 33 an output is present in the outputport 35 and when a predetermined input pressure is in the input port 33and the output does not appear in the output port 35.

Operation of the apparatus of the above construction is now describedbelow. Before starting of operation, the changeover valves 13 and 81 inthe apparatus are not in a communicated state while the changeover valve86 is in a communicated state. At the start of operation of theapparatus, the manual operation changeover valve 81 is changed to becommunicated. As the changeover valve 81 is changed, the pressure airsupplied from the pipe is supplied, through the OR gate 82, pipe andchangeover valve 86, to the supply port 32 of the device 31.

As illustrated in reference to FIGS. 2 and 3, before starting of theliquid supply, the air pressure Pc of the input port 33 is at P00 whichis below the critical value Pcc. Therefore, the compressed air suppliedto the supply port 32 from the pipe 85 is taken out as an output fromthe output port 35 and supplied through the pipe 101 to the pilot part21 of the changeover valve 13. Then, the changeover valve 13 is changedto be communicated. The compressed air from the pipe 1 1 is supplied,through the changeover valve 13 and pipe 83, to a liquid supplyoperating valve 88 which is then opened. The liquid is thereby startedto flow through the pipe 87 and loading arm 91.

With the changeover valve 13 being communicated and the pipe 83 passedwith compressed air, a part of the compressed air passes through thepipe 84 and is supplied to the OR gate 82. There is thus formed a closedloop including the changeover valve 13-pipe 83-pipe 84-OR gate 82-pipe85changeover valve 86-signal amplifier changing part 15-pipe 20-pilotpart 21 of the changeover valve 13. Therefore, if the manual operationchangeover valve 81 is automatically returned to its non-communicatedcondition after operation, the changeover valve 13 is self-held in itscommunicated condition. The indicator 89 operates when it is suppliedcompressed air through the pipes 83 and 90. The indicator 90 indicatesthe opening of the operating valve 88.

With the progress of liquid supply and reaching of the head height h ofthe liquid 25 to the critical value he, the pressure Pc of the inputport 33 attains the criti cal value Pcc. At this instant, the output ofthe device 31 is changed from the output port 35 to the output port 34.The output pressure P of the output port 35 is digitally changed to zeroas shown in FIG. 11. As the output of the port 35 is at zero, the pilotpart 21 of the changeover valve 13 is not supplied air pressure. Thechangeover valve 13 returns to its initial condition as shown in FIG. 9and intercepts the communication of the pipes 11 and 83. Therefore, theliquid supply operating valve 88 is not supplied the compressed air butclosed to stop the liquid supply. At the same time, the indicator 89 isnot supplied the compressed air and indicates the closing of theoperating valve 88.

During the liquid supply operation as above described, the liquid supplyis sometimes required to be stopped in emergency. Then, an emergencystop manual operation changeover valve 86 may be operated to take anon-communicated condition. By this operation, the pipe 85 isinterrupted and the pressure air is' not supplied to the pilot part 21so that the changeover valve 13 returns to a non-communicatingcondition. In the similar way, the operating valve 88 is closed. Theliquid supply is urgently stopped so as to meet the emergency.

For the liquid level detecting part 14 of the above embodiment as shownin FIG. 9, the detecting part as described in reference to FIGS. 4 and 6can be employed. When the liquid level detecting part of FIG. 4 isemployed, the air pipe extending to the pilot part 21 of the changeovervalve 13 is connected to the output port 34 of the device 31. Also, whenthe liquid level detecting part of FIG. 6 is employed, the air pipeextending to the pilot part 21 of the changeover valve 13 and isconnected to the output port 35 of the device 31.

A third embodiment of the apparatus according to the present inventionis shown in FIG. 12. lnFIGS. 9 and 12, identical parts are denotedby thesame numerals, the illustration thereof being therefore omitted.

A NOT device 110 is provided in the way of the air pipe 20 extendingfrom the signalamplifier changeover part to the pilot part 21 of thechangeover valve 13. The NOT device consists of a pure fluidic device.When no input signal is present in an input port 111 of the device 110,the compressed air supplied from the pipe to a supply port 112 is takenout as an output from an output port 113. When the input signal ispresent in the input port 1 1 1, output does not appear in the outputport 113. I

There is provided a flowmeter 114 in the liquid pipe 87. The NOTquantity of liquid is delivered to a fixed quantity signal emissionmechanism 115 and a printer 1 16. The fixed quantity signal emissionmechanism 1 15 sends a fixed quantity air signal to the not device 110when the flow quantity of the liquid measured by the flowmeter 114 andpassed through the pipe 87 reaches a predetermined quantity. The fixedquantity signal emission mechanism may have its own air source or usethe air from the air source 10. The above-mentioned changeover valves13, 81 and 86, OR gate 82 signal amplifier changeover part 15, NOTdevice 110, v

and indicator 89 are all contained in a control box 118. A manualoperation valve 117 is provided for stopping the liquid supply manuallyupon emergency when the air operating valve 88 has some troubles.

Similarly as in the above embodiment, the liquid supply operation isstarted. Before the liquid surface level of the liquid 25 reaches apredetermined level so as to operate the liquid level detecting part 14,when the liquid quantity may reach a fixed value as previously set up,the fixed quantity signal emission mechanism 115 sends an air signal tothe NOT device 110. Output is not appeard at the output port'113 of theNOT device 110. The changeover valve 113 is changed. The operating valve88 is closed and the liquid supply is stopped. The quantity of thesupplied liquid is printed on a bill by the printer 116.

If some previous liquid remains previously in the tank 19, the level ofthe liquid in the tank 19 sometimes reaches a fixed critical levelbefore the quantity .of liquid supply reaches a fixed value. Similarly,in case a trouble occurs in the system of the fixed quantity signalemission mechanism 1 15, the liquid level would reach a critical level.At this instant, the level sensor 17 of the liquid level detecting part14 detects the liquid level reaching a critical level and stops theliquid supply by operation similar to the above described embodiments.Consequently, the overflow of the liquid 25 canbe avoided for the tank19.

In the above second and third embodiments, the.

operating valve 88 is a normally-closed'valve to open while thecompressed air is being supplied. However, this operating valve 88 maybe a normally opened valve to close when the compressed air is supplied.In this event, other open-close valve is provided in the fuel supplypipe 87 and the operating valve 88 may be used exclusively as a stopvalve. Also, in this case, the chan geover valve 13 remains in anon-communicating condition during the liquid supplying operation. Thede-: tecting parts as shown in FIGS. 2, 4 and 6 may be used as theliquid level detecting part14.

As embodiments of the control boxes 24, 92 and 118 may be fixedlyprovided on the side of the liquid supply equipment or on the side ofthe container for receiving the liquid supplysuch as a tank lorry, orotherwise constructed in a portable type. The air source 10 may beprovided at the container side such as tank lorry or constructed in theportable type. The embodiments of the control boxes and air sources maydesirably formed in suitable combinations.

FIG. 13 shows two actual embodiments in which the 123a and loading arm91a. A control box 124 contain-. ing the signal amplifier changeoverpart of the liquid level sensing part according to this invention isfixed at the tank lorry 18a. A level senser 125 inserted into the tank190 and the control box 124 are connected by an air pipe 126. Thecontrol box 124 is supplied with compressed air through a flexible airpipe 128 from an air compressor 127. As the supply of the liquid 25advances and the level senser 125 detects the liquid level being reachedas predetermined, an alarm 129 of the control box 124 sounds by similaroperation as hereinabove described.

In a tank 19b of the tank lorry 18b stationed on the right side of theliquid supplying stage 120 there is, as shown in the figure, inserted anend of a loading arm 91b and a level sensor. A control box 130 whichcontains a signal amplifier changeover part of a liquid level detectingpart is provided in the way of a fixed liquid supply pipe 121b. Thecontrol box 130 and the level senser in the tank 19b are connected by aflexible air pipe 131. The control box 130 and an operating part 133 ofan operating valve 123b are connected by an air pipe 132. When the levelsenser detects that the level of the supplied liquid has reached apredetermined level of liquid, the operating valve 12312 is closed.

Throughout these embodiments, the compressed air source to the controlboxes 124 and 130 is applied the compressor 127. The compressed airhowever may be supplied from an air tank for air braking, if the airtank is provided in the tank lorry.

FIG. 14 shows a practical embodiment of the apparatus of this inventionwhich is used in a gasoline filling service station.

A gasoline reservoir 140 is provided in the underground of the servicearea of a fuel supplying station. In normal fuel supplying operation,gasoline is suctioned from the reservoir tank 140 by a pump 142 which isdriven by a motor 141. The suctioned gasoline passes through a fixedpipe 145 provided in walls 143 and the ceiling 144 and runs to adelivery unit 146. During the fuel supplying operation, a flexible pipe147 is pulled down from the delivery unit 146. Fuel supply is made froma nozzle 148 provided at the end of the delivery unit.

Upon supplying fuel to the reservoir tank 140 of the fuel supplyingstation, it is usual to supply fuel from the tank 150 of the tank lorry149 filled with gasoline by means of a hose 151. A control box 152containing the signal amplifier changeover part of the liquid leveldetecting part according to this invention has a construction designedin a portable type which is desirably carried about. The tank 140 isinserted with a level sensor 153 which can be adjusted of its height.The control box 152 and the level sensor 153 are connected by a rubberhose 154. Also, the control box 152 is connected to a liquid supplyoperating valve 156 by a rubber hose 155. On the backside of the walls143 is placed a compressor 157. For supplying compressed air of thecompressor 157, a coupling port 158 is provided at a front surface ofthe walls 143. The coupling port 158 and the control box 152 areconnected by a rubber hose 159. The control box 152 is suppliedcompressed air form the compressor 157. When the level sensor 153detects that the liquid level has reached the predetermined level, theoperating valve 156 is closed and the fuel supply to the tank 140 isstopped. Instead of or at the same time as the operation of stopping theliquid supply, there may be provided a construction which allows thealarm on the control box 152 to sound.

In the embodiments shown in the above, the device 31 may consist of apure fluidic device which may otherwise be a moving type fluidic deviceor amplifier.

What we claim is:

l. A liquid level detecting apparatus comprising a compressed airsource; a fluidic device having a supply port supplied with compressedair from the compressed air source, an input port and output port; aliquid level sensing means, said sensing means being'supplied withcompressed air from said compressed air source and providing a pressurecontrolled by the exhaustion of said compressed air to the atmosphereresponsive to the level of the liquid, the liquid level dependentpressure in said sensing means being supplied to the input port of thefluidic device; an air-operated changeover valve which is changed overby variation of output of the fluidic device; and an operating meansvariable in its condition by the changing of output of the fluidicdevice, wherein said output of the output port of the fluidic device ischanged over by the input air pressure supplied to the input port, andsaid operating means is supplied with the compressed air from thecompressed air source through the changeover valve.

2. The apparatus of claim 1, in which said liquid level sensing meanscomprises a first nozzle supplied with the compressed air from thecompressed air source and jetting the air into the atmosphere, a secondnozzle connected to the input port of the fluidic device and having itsjetting port opposite to the first nozzle, an air pipe communicatingbetween the first and second nozzles through a pressure reducing valve,and a shield plate floating on the liquid and movable upwardly anddownwardly responsive to the liquid level, said shield plate beingcapable of locating between the first and second nozzles, said inputport receiving the input from the air pipe when the shield plate is notlocated between the first and second nozzles but not receiving the inputwhen the shield plate is located between the first and second nozzles.

3. The apparatus of claim 1, which further comprises an OR gate meanscommunicating with the compressed air source side and the output side ofthe changeover valve and producing an output when the compressed air ispresent at least in either one of the compressed air source side or theoutput side of the changeover valve, wherein said operating means is aliquid supply operating valve provided in a liquid supply pipe to openwhile it receives the compressed air, said changeover valve beingprovided between the compressed air source and the operating valve, saidoutput of the fluidic device is changed over so as to change thechangeover valve to non-communicating condition when the liquid levelsensing means senses a liquid level as predetermined, said OR gate meansmaking self-holding of communication of the changeover valve.

4. The apparatus of claim 3, which further comprises a flowrneterprovided in the liquid supply pipe, a fixed quantity signal emissionmeans cooperating with the flowmeter and emitting a fixed quantity airsignal when the flow quantity reaches a predetermined quantity and a NOTdevice being interposed between the output side of the fluidic deviceand the changeover valve and perquantity signal emission means.

5. The apparatus of claim 1 in which said operating means is an alarmmeans operated by the compressed air from the compressed air sourcethrough the changeover valve, and said output of the fluidic device ischanged over to changeover the air-operated changeover valve so that thealarm means is operated by the compressed air when the liquid levelsensing means detects a predetermined liquid level.

6. The apparatus of claim 1 in which said operating means is anopen-close valve provided in a liquid supply pipe and operated by thethe compressed air

1. A liquid level detecting apparatus comprising a compressed airsource; a fluidic device having a supply port supplied with compressedair from the compressed air source, an input port and output port; aliquid level sensing means, said sensing means being supplied withcompressed air from said compressed air source and providing a pressurecontrolled by the exhaustion of said compressed air to the atmosphereresponsive to the level of the liquid, the liquid level dependentpressure in said sensing means being supplied to the input port of thefluidic device; an air-operated changeover valve which is changed overby variation of output of the fluidic device; and an operating meansvariable in its condition by the changing of output of the fluidicdevice, wherein said output of the output port of the fluidic device ischanged over by the input air pressure supplied to the input port, andsaid operating means is supplied with the compressed air from thecompressed air source through the changeover valve.
 2. The apparatus ofclaim 1, in which said liquid level sensing means comprises a firstnozzle supplied with the compressed air from the compressed air sourceand jetting the air into the atmosphere, a second nozzle connected tothe input port of the fluidic device and having its jetting portopposite to the first nozzle, an air pipe communicating between thefirst and second nozzles through a pressure reducing valve, and a shieldplate floating on the liquid and movable upwardly and downwardlyresponsive to the liquid level, said shield plate being capable oflocating between the first and second nozzles, said input port receivingthe input from the air pipe when the shield plate is not located betweenthe first and second nozzles but not receiving the input when the shieldplate is located between the first and second nozzles.
 3. The apparatusof claim 1, which further comprises an OR gate means communicating withthe compressed air source side and the output side of the changeovervalve and producing an output when the compressed air is present atleast in either one of the compressed air source side or the output sideof the changeover valve, wherein said operating means is a liquid supplyoperating valve provided in a liquid supply pipe to open while itreceives the compressed air, said changeover valve being providedbetween the compressed air source and the operating valve, said outputof the fluidic device is changed over so as to change the changeovervalve to non-communicating condition when the liquid level sensing meanssenses a liquid level as predetermined, said OR gate means makingself-holding of communication of the changeover valve.
 4. The apparatusof claim 3, which further comprises a flowmeter provided in the liquidsupply pipe, a fixed quantity signal emission means cooperating with theflowmeter and emitting a fixed quantity air signal when the flowquantity reaches a predetermined quantity and a NOT device beinginterposed between the output side of the fluidic device and thechangeover valve and performing a NOT operation by the signal from thefixed quantity signal emission means.
 5. The apparatus of claim 1 inwhich said operating means is an alarm means operated by the compressedair from the compressed air source through the changeover valve, andsaid output of the fluidic device is changed over to changeover theair-operated changeover valve so that the alarm means is operated by thecompressed air when the liquid level sensing means detects apredetermined liquid level.
 6. The apparaTus of claim 1 in which saidoperating means is an open-close valve provided in a liquid supply pipeand operated by the the compressed air from the compressed air sourcethrough the changeover valve, and said output of the fluidic device ischanged over to change over the air-operated changeover valve so thatthe open-close valve is closed by the compressed air when the liquidlevel sensing means detects a predetermined liquid level.